* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
+#define _ISOC99_SOURCE /* for round() */
+#define _XOPEN_SOURCE 500
+
#include "acre.h"
#include "xmalloc.h"
cairo_restore (cr);
}
+/* For a given axis range, compute a step size (in data space) to
+ * generate a suitable number of ticks (5 or so). */
+static double
+_step_for_range (double range)
+{
+ double step, scale_factor;
+
+ /* We want roughly 5 major ticks for the chart. */
+ step = range / 5;
+
+ /* Normalize the step so we can easily snap it to a desirable
+ * value. */
+ scale_factor = pow (10.0, floor (log10 (step)));
+ step /= scale_factor;
+
+ /* We want increments of 1, 2.5, 5, or 10 (times some power of
+ * 10). The threshold values between these are computed
+ * logarithmically. */
+ if (step < 3.535533905932738) {
+ if (step < 1.58113883008419)
+ step = 1.0;
+ else
+ step = 2.5;
+ } else {
+ if (step < 7.071067811865475)
+ step = 5.0;
+ else
+ step = 10.0;
+ }
+
+ /* Un-normalize and we now have the data value that we want to
+ * step at. */
+ return step * scale_factor;
+}
+
+/* Given an axis range, we can compute a desired data-space step
+ * amount for the major ticks (see _step_for_range). To get
+ * nice-looking pixel-snapped ticks we want to expand the range
+ * slightly. */
+static void
+_expand_range_for_width (double *axis_min, double *axis_max, int pixel_size)
+{
+ double range, new_range, step, pixel_step;
+
+ range = *axis_max - *axis_min;
+
+ step = _step_for_range (range);
+ pixel_step = step * pixel_size / range;
+
+ /* We expand the range by the ratio of the pixel step to the floor
+ * of the pixel_step.
+ */
+ new_range = range * pixel_step / floor (pixel_step);
+
+ /* And spread the increase out on either side of the range. */
+ *axis_min -= (new_range - range) / 2.0;
+ *axis_max += (new_range - range) / 2.0;
+}
+
+/* Setup a transformation in acre->cr such that data values plotted
+ * will appear where they should within the chart.
+ */
+static void
+_set_transform_to_data_space (acre_t *acre)
+{
+ cairo_t *cr = acre->cr;
+
+ cairo_translate (cr,
+ acre->chart.x,
+ acre->chart.y + acre->chart.height);
+ cairo_scale (cr,
+ acre->chart.width / (acre->x_axis.max - acre->x_axis.min),
+ - acre->chart.height /(acre->y_axis.max - acre->y_axis.min));
+ cairo_translate (cr, -acre->x_axis.min, -acre->y_axis.min);
+}
+
static void
_compute_axis_ranges (acre_t *acre)
{
unsigned int d, i;
acre_data_t *data;
+ double x_adjust, y_adjust;
+ cairo_t *cr = acre->cr;
+ /* First, simply find the extrema of the data. */
for (d = 0; d < acre->num_data; d++) {
data = acre->data[d];
for (i = 0; i < data->num_points; i++) {
acre->y_axis.max = data->points[i].y;
}
}
-}
-/* Setup a transformation in acre->cr such that data values plotted
- * will appear where they should within the chart.
- */
-static void
-_set_transform_to_data_space (acre_t *acre)
-{
- cairo_t *cr = acre->cr;
+ /* Next, increase the axis ranges just enough so that the step
+ * sizes for the ticks will be integers.
+ */
+ _expand_range_for_width (&acre->x_axis.min,
+ &acre->x_axis.max,
+ acre->chart.width);
- cairo_translate (cr,
- acre->chart.x,
- acre->chart.y + acre->chart.height);
- cairo_scale (cr,
- acre->chart.width / (acre->x_axis.max - acre->x_axis.min),
- - acre->chart.height /(acre->y_axis.max - acre->y_axis.min));
- cairo_translate (cr, -acre->x_axis.min, -acre->y_axis.min);
+ _expand_range_for_width (&acre->y_axis.min,
+ &acre->y_axis.max,
+ acre->chart.height);
+
+ /* Finally, we also translate the axis ranges slightly so that the
+ * ticks land on half-integer device-pixel positions.
+ */
+ cairo_save (cr);
+ {
+ _set_transform_to_data_space (acre);
+
+ x_adjust = 0.0;
+ y_adjust = 0.0;
+ cairo_user_to_device (cr, &x_adjust, &y_adjust);
+ x_adjust = (round (x_adjust + 0.5) - 0.5) - x_adjust;
+ y_adjust = (round (y_adjust + 0.5) - 0.5) - y_adjust;
+ cairo_device_to_user_distance (cr, &x_adjust, &y_adjust);
+
+ acre->x_axis.min -= x_adjust;
+ acre->x_axis.max -= x_adjust;
+
+ acre->y_axis.min -= y_adjust;
+ acre->y_axis.max -= y_adjust;
+ }
+ cairo_restore (cr);
}
static void
cairo_restore (cr);
}
-static double
-_step_for_range (double range)
-{
- double step, scale_factor;
-
- /* We want roughly 5 major ticks for the chart. */
- step = range / 5;
-
- /* Normalize the step so we can easily snap it to a desirable
- * value. */
- scale_factor = pow (10.0, floor (log10 (step)));
- step /= scale_factor;
-
- /* We want increments of 1, 2.5, 5, or 10 (times some power of
- * 10). The threshold values between these are computed
- * logarithmically. */
- if (step < 3.535533905932738) {
- if (step < 1.58113883008419)
- step = 1.0;
- else
- step = 2.5;
- } else {
- if (step < 7.071067811865475)
- step = 5.0;
- else
- step = 10.0;
- }
-
- /* Un-normalize and we now have the data value that we want to
- * step at. */
- return step * scale_factor;
-}
-
static void
_draw_frame_and_ticks (acre_t *acre)
{
{
cairo_identity_matrix (cr);
cairo_rel_line_to (cr, 0, 0.5);
- cairo_rel_line_to (cr, 0, -ACRE_TICK_SIZE);
+ cairo_rel_line_to (cr, 0, -ACRE_TICK_SIZE-0.5);
cairo_set_line_width (cr, 1.0);
cairo_stroke (cr);
}
{
cairo_identity_matrix (cr);
cairo_rel_line_to (cr, -0.5, 0);
- cairo_rel_line_to (cr, ACRE_TICK_SIZE, 0);
+ cairo_rel_line_to (cr, ACRE_TICK_SIZE+0.5, 0);
cairo_set_line_width (cr, 1.0);
cairo_stroke (cr);
}
projects / acre / blobdiff